1. Field of the Invention
The present invention relates to a device for repeated registration of the number of thermal cycles to which a part for medical usage has been subjected.
2. Description of the Prior Art
A large number of parts or components in medical devices require sterilization between each use. This is often accomplished by heating the part or component in an autoclave. For safety reasons, these parts or components may not be reused more than a limited number of times. Therefore, careful monitoring and reliable, tamper-proof checking of the number of times parts and components are reused are very important. The number of times a part has been autoclaved has hitherto often been determined by using a logbook, a technique which can vary as to reliability.
U.S. Pat. No. 5,383,874 describes a system for identifying and monitoring the use of ablation catheters. This system employs a usage register, whose contents are incremented by one every time the catheter is put to authorized use, to ensure that the catheter is not used too frequently.
German 05 19825 754 (corresponding to co-pending U.S. application Ser. No. 09/098,495 filed Jun. 17, 1998) describes a device for counting the number of usage cycles by a sensor for intracorporeal electrophysiological measurement and/or therapy. Here, a counter connected to the sensor contains an identification code specific to the sensor, and connection! disconnection of the sensor to/from external measurement equipment and/or therapeutic equipment is detected. The identification code is used for determining, from information stored in a main computer on previous usage, whether conditions for a new usage cycle have been met and, if so, incrementing counter contents by one usage cycle.
Another system for counting usage cycles is disclosed in U.S. Pat. No. 5,400,267.
Disinfecting indicators are also known, as described in U.S. Pat. No. 4,449,518 which discloses such an indicator using a memory alloy. The indicator is deformed when the device is used and re-assumes its shape when exposed to heat. This system does not register the number of disinfecting or heat cycles.
U.S. Pat. Nos. 5,313,935; 5,359,993; and 5,452,335 and European Application 581 400 all essentially show devices for indicating the number of thermal cycles by moving a cog wheel one step for each cycle. On the cogs, indicator numbers are placed. Through a window of the indicator numbers can be viewed, indicating a present number of thermal cycles. However, none of these devices can indicate whether the device has gone through a thermal cycle before a new use of the device. Since the indicator numbers are placed on the cogwheels, the total number of thermal cycles is limited to fairly low numbers. This because the indicator numbers must be significantly large for a user to read.
The ability to distinguished sterilized replaceable items from unsterilized items is also of the greatest importance in this field. At present, unsterilized and sterilized components are usually stored at different locations, but mix-ups may occur because the appearance of an item does not indicate whether the item has been sterilized.